﻿// llvm.cpp: 定义应用程序的入口点。
//

#include "llvm.h"
#include "KaleidoscopeJIT.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Passes/PassBuilder.h"
#include "llvm/Passes/StandardInstrumentations.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/InstCombine/InstCombine.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Scalar/GVN.h"
#include "llvm/Transforms/Scalar/Reassociate.h"
#include "llvm/Transforms/Scalar/SimplifyCFG.h"
#include <algorithm>
#include <cassert>
#include <cctype>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <map>
#include <memory>
#include <string>
#include <vector>

using namespace llvm;
using namespace llvm::orc;

//===----------------------------------------------------------------------===//
// Lexer
//===----------------------------------------------------------------------===//

// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
// of these for known things.
enum Token {
    tok_eof = -1,

    // commands
    tok_def = -2,
    tok_extern = -3,

    // primary
    tok_identifier = -4,
    tok_number = -5,

    // control
    tok_if = -6,
    tok_then = -7,
    tok_else = -8,
    tok_for = -9,
    tok_in = -10
};

static std::string IdentifierStr; // Filled in if tok_identifier
static double NumVal;             // Filled in if tok_number

/// gettok - Return the next token from standard input.
static int gettok() {
    static int LastChar = ' ';

    // Skip any whitespace.
    while (isspace(LastChar))
        LastChar = getchar();

    if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
        IdentifierStr = LastChar;
        while (isalnum((LastChar = getchar())))
            IdentifierStr += LastChar;

        if (IdentifierStr == "def")
            return tok_def;
        if (IdentifierStr == "extern")
            return tok_extern;
        if (IdentifierStr == "if")
            return tok_if;
        if (IdentifierStr == "then")
            return tok_then;
        if (IdentifierStr == "else")
            return tok_else;
        if (IdentifierStr == "for")
            return tok_for;
        if (IdentifierStr == "in")
            return tok_in;
        return tok_identifier;
    }

    if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
        std::string NumStr;
        do {
            NumStr += LastChar;
            LastChar = getchar();
        } while (isdigit(LastChar) || LastChar == '.');

        NumVal = strtod(NumStr.c_str(), nullptr);
        return tok_number;
    }

    if (LastChar == '#') {
        // Comment until end of line.
        do
            LastChar = getchar();
        while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');

        if (LastChar != EOF)
            return gettok();
    }

    // Check for end of file.  Don't eat the EOF.
    if (LastChar == EOF)
        return tok_eof;

    // Otherwise, just return the character as its ascii value.
    int ThisChar = LastChar;
    LastChar = getchar();
    return ThisChar;
}

//===----------------------------------------------------------------------===//
// Abstract Syntax Tree (aka Parse Tree)
//===----------------------------------------------------------------------===//

namespace {

    /// ExprAST - Base class for all expression nodes.
    class ExprAST {
    public:
        virtual ~ExprAST() = default;

        virtual Value* codegen() = 0;
    };

    /// NumberExprAST - Expression class for numeric literals like "1.0".
    class NumberExprAST : public ExprAST {
        double Val;

    public:
        NumberExprAST(double Val) : Val(Val) {}

        Value* codegen() override;
    };

    /// VariableExprAST - Expression class for referencing a variable, like "a".
    class VariableExprAST : public ExprAST {
        std::string Name;

    public:
        VariableExprAST(const std::string& Name) : Name(Name) {}

        Value* codegen() override;
    };

    /// BinaryExprAST - Expression class for a binary operator.
    class BinaryExprAST : public ExprAST {
        char Op;
        std::unique_ptr<ExprAST> LHS, RHS;

    public:
        BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
            std::unique_ptr<ExprAST> RHS)
            : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}

        Value* codegen() override;
    };

    /// CallExprAST - Expression class for function calls.
    class CallExprAST : public ExprAST {
        std::string Callee;
        std::vector<std::unique_ptr<ExprAST>> Args;

    public:
        CallExprAST(const std::string& Callee,
            std::vector<std::unique_ptr<ExprAST>> Args)
            : Callee(Callee), Args(std::move(Args)) {}

        Value* codegen() override;
    };

    /// IfExprAST - Expression class for if/then/else.
    class IfExprAST : public ExprAST {
        std::unique_ptr<ExprAST> Cond, Then, Else;

    public:
        IfExprAST(std::unique_ptr<ExprAST> Cond, std::unique_ptr<ExprAST> Then,
            std::unique_ptr<ExprAST> Else)
            : Cond(std::move(Cond)), Then(std::move(Then)), Else(std::move(Else)) {}

        Value* codegen() override;
    };

    /// ForExprAST - Expression class for for/in.
    class ForExprAST : public ExprAST {
        std::string VarName;
        std::unique_ptr<ExprAST> Start, End, Step, Body;

    public:
        ForExprAST(const std::string& VarName, std::unique_ptr<ExprAST> Start,
            std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
            std::unique_ptr<ExprAST> Body)
            : VarName(VarName), Start(std::move(Start)), End(std::move(End)),
            Step(std::move(Step)), Body(std::move(Body)) {}

        Value* codegen() override;
    };

    /// PrototypeAST - This class represents the "prototype" for a function,
    /// which captures its name, and its argument names (thus implicitly the number
    /// of arguments the function takes).
    class PrototypeAST {
        std::string Name;
        std::vector<std::string> Args;

    public:
        PrototypeAST(const std::string& Name, std::vector<std::string> Args)
            : Name(Name), Args(std::move(Args)) {}

        Function* codegen();
        const std::string& getName() const { return Name; }
    };

    /// FunctionAST - This class represents a function definition itself.
    class FunctionAST {
        std::unique_ptr<PrototypeAST> Proto;
        std::unique_ptr<ExprAST> Body;

    public:
        FunctionAST(std::unique_ptr<PrototypeAST> Proto,
            std::unique_ptr<ExprAST> Body)
            : Proto(std::move(Proto)), Body(std::move(Body)) {}

        Function* codegen();
    };

} // end anonymous namespace

//===----------------------------------------------------------------------===//
// Parser
//===----------------------------------------------------------------------===//

/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
/// token the parser is looking at.  getNextToken reads another token from the
/// lexer and updates CurTok with its results.
static int CurTok;
static int getNextToken() { return CurTok = gettok(); }

/// BinopPrecedence - This holds the precedence for each binary operator that is
/// defined.
static std::map<char, int> BinopPrecedence;

/// GetTokPrecedence - Get the precedence of the pending binary operator token.
static int GetTokPrecedence() {
    if (!isascii(CurTok))
        return -1;

    // Make sure it's a declared binop.
    int TokPrec = BinopPrecedence[CurTok];
    if (TokPrec <= 0)
        return -1;
    return TokPrec;
}

/// LogError* - These are little helper functions for error handling.
std::unique_ptr<ExprAST> LogError(const char* Str) {
    fprintf(stderr, "Error: %s\n", Str);
    return nullptr;
}

std::unique_ptr<PrototypeAST> LogErrorP(const char* Str) {
    LogError(Str);
    return nullptr;
}

static std::unique_ptr<ExprAST> ParseExpression();

/// numberexpr ::= number
static std::unique_ptr<ExprAST> ParseNumberExpr() {
    auto Result = std::make_unique<NumberExprAST>(NumVal);
    getNextToken(); // consume the number
    return std::move(Result);
}

/// parenexpr ::= '(' expression ')'
static std::unique_ptr<ExprAST> ParseParenExpr() {
    getNextToken(); // eat (.
    auto V = ParseExpression();
    if (!V)
        return nullptr;

    if (CurTok != ')')
        return LogError("expected ')'");
    getNextToken(); // eat ).
    return V;
}

/// identifierexpr
///   ::= identifier
///   ::= identifier '(' expression* ')'
static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
    std::string IdName = IdentifierStr;

    getNextToken(); // eat identifier.

    if (CurTok != '(') // Simple variable ref.
        return std::make_unique<VariableExprAST>(IdName);

    // Call.
    getNextToken(); // eat (
    std::vector<std::unique_ptr<ExprAST>> Args;
    if (CurTok != ')') {
        while (true) {
            if (auto Arg = ParseExpression())
                Args.push_back(std::move(Arg));
            else
                return nullptr;

            if (CurTok == ')')
                break;

            if (CurTok != ',')
                return LogError("Expected ')' or ',' in argument list");
            getNextToken();
        }
    }

    // Eat the ')'.
    getNextToken();

    return std::make_unique<CallExprAST>(IdName, std::move(Args));
}

/// ifexpr ::= 'if' expression 'then' expression 'else' expression
static std::unique_ptr<ExprAST> ParseIfExpr() {
    getNextToken(); // eat the if.

    // condition.
    auto Cond = ParseExpression();
    if (!Cond)
        return nullptr;

    if (CurTok != tok_then)
        return LogError("expected then");
    getNextToken(); // eat the then

    auto Then = ParseExpression();
    if (!Then)
        return nullptr;

    if (CurTok != tok_else)
        return LogError("expected else");

    getNextToken();

    auto Else = ParseExpression();
    if (!Else)
        return nullptr;

    return std::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
        std::move(Else));
}

/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
static std::unique_ptr<ExprAST> ParseForExpr() {
    getNextToken(); // eat the for.

    if (CurTok != tok_identifier)
        return LogError("expected identifier after for");

    std::string IdName = IdentifierStr;
    getNextToken(); // eat identifier.

    if (CurTok != '=')
        return LogError("expected '=' after for");
    getNextToken(); // eat '='.

    auto Start = ParseExpression();
    if (!Start)
        return nullptr;
    if (CurTok != ',')
        return LogError("expected ',' after for start value");
    getNextToken();

    auto End = ParseExpression();
    if (!End)
        return nullptr;

    // The step value is optional.
    std::unique_ptr<ExprAST> Step;
    if (CurTok == ',') {
        getNextToken();
        Step = ParseExpression();
        if (!Step)
            return nullptr;
    }

    if (CurTok != tok_in)
        return LogError("expected 'in' after for");
    getNextToken(); // eat 'in'.

    auto Body = ParseExpression();
    if (!Body)
        return nullptr;

    return std::make_unique<ForExprAST>(IdName, std::move(Start), std::move(End),
        std::move(Step), std::move(Body));
}

/// primary
///   ::= identifierexpr
///   ::= numberexpr
///   ::= parenexpr
///   ::= ifexpr
///   ::= forexpr
static std::unique_ptr<ExprAST> ParsePrimary() {
    switch (CurTok) {
    default:
        return LogError("unknown token when expecting an expression");
    case tok_identifier:
        return ParseIdentifierExpr();
    case tok_number:
        return ParseNumberExpr();
    case '(':
        return ParseParenExpr();
    case tok_if:
        return ParseIfExpr();
    case tok_for:
        return ParseForExpr();
    }
}

/// binoprhs
///   ::= ('+' primary)*
static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
    std::unique_ptr<ExprAST> LHS) {
    // If this is a binop, find its precedence.
    while (true) {
        int TokPrec = GetTokPrecedence();

        // If this is a binop that binds at least as tightly as the current binop,
        // consume it, otherwise we are done.
        if (TokPrec < ExprPrec)
            return LHS;

        // Okay, we know this is a binop.
        int BinOp = CurTok;
        getNextToken(); // eat binop

        // Parse the primary expression after the binary operator.
        auto RHS = ParsePrimary();
        if (!RHS)
            return nullptr;

        // If BinOp binds less tightly with RHS than the operator after RHS, let
        // the pending operator take RHS as its LHS.
        int NextPrec = GetTokPrecedence();
        if (TokPrec < NextPrec) {
            RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
            if (!RHS)
                return nullptr;
        }

        // Merge LHS/RHS.
        LHS =
            std::make_unique<BinaryExprAST>(BinOp, std::move(LHS), std::move(RHS));
    }
}

/// expression
///   ::= primary binoprhs
///
static std::unique_ptr<ExprAST> ParseExpression() {
    auto LHS = ParsePrimary();
    if (!LHS)
        return nullptr;

    return ParseBinOpRHS(0, std::move(LHS));
}

/// prototype
///   ::= id '(' id* ')'
static std::unique_ptr<PrototypeAST> ParsePrototype() {
    if (CurTok != tok_identifier)
        return LogErrorP("Expected function name in prototype");

    std::string FnName = IdentifierStr;
    getNextToken();

    if (CurTok != '(')
        return LogErrorP("Expected '(' in prototype");

    std::vector<std::string> ArgNames;
    while (getNextToken() == tok_identifier)
        ArgNames.push_back(IdentifierStr);
    if (CurTok != ')')
        return LogErrorP("Expected ')' in prototype");

    // success.
    getNextToken(); // eat ')'.

    return std::make_unique<PrototypeAST>(FnName, std::move(ArgNames));
}

/// definition ::= 'def' prototype expression
static std::unique_ptr<FunctionAST> ParseDefinition() {
    getNextToken(); // eat def.
    auto Proto = ParsePrototype();
    if (!Proto)
        return nullptr;

    if (auto E = ParseExpression())
        return std::make_unique<FunctionAST>(std::move(Proto), std::move(E));
    return nullptr;
}

/// toplevelexpr ::= expression
static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
    if (auto E = ParseExpression()) {
        // Make an anonymous proto.
        auto Proto = std::make_unique<PrototypeAST>("__anon_expr",
            std::vector<std::string>());
        return std::make_unique<FunctionAST>(std::move(Proto), std::move(E));
    }
    return nullptr;
}

/// external ::= 'extern' prototype
static std::unique_ptr<PrototypeAST> ParseExtern() {
    getNextToken(); // eat extern.
    return ParsePrototype();
}

//===----------------------------------------------------------------------===//
// Code Generation
//===----------------------------------------------------------------------===//

static std::unique_ptr<LLVMContext> TheContext;
static std::unique_ptr<Module> TheModule;
static std::unique_ptr<IRBuilder<>> Builder;
static std::map<std::string, Value*> NamedValues;
static std::unique_ptr<KaleidoscopeJIT> TheJIT;
static std::unique_ptr<FunctionPassManager> TheFPM;
static std::unique_ptr<LoopAnalysisManager> TheLAM;
static std::unique_ptr<FunctionAnalysisManager> TheFAM;
static std::unique_ptr<CGSCCAnalysisManager> TheCGAM;
static std::unique_ptr<ModuleAnalysisManager> TheMAM;
static std::unique_ptr<PassInstrumentationCallbacks> ThePIC;
static std::unique_ptr<StandardInstrumentations> TheSI;
static std::map<std::string, std::unique_ptr<PrototypeAST>> FunctionProtos;
static ExitOnError ExitOnErr;

Value* LogErrorV(const char* Str) {
    LogError(Str);
    return nullptr;
}

Function* getFunction(std::string Name) {
    // First, see if the function has already been added to the current module.
    if (auto* F = TheModule->getFunction(Name))
        return F;

    // If not, check whether we can codegen the declaration from some existing
    // prototype.
    auto FI = FunctionProtos.find(Name);
    if (FI != FunctionProtos.end())
        return FI->second->codegen();

    // If no existing prototype exists, return null.
    return nullptr;
}

Value* NumberExprAST::codegen() {
    return ConstantFP::get(*TheContext, APFloat(Val));
}

Value* VariableExprAST::codegen() {
    // Look this variable up in the function.
    Value* V = NamedValues[Name];
    if (!V)
        return LogErrorV("Unknown variable name");
    return V;
}

Value* BinaryExprAST::codegen() {
    Value* L = LHS->codegen();
    Value* R = RHS->codegen();
    if (!L || !R)
        return nullptr;

    switch (Op) {
    case '+':
        return Builder->CreateFAdd(L, R, "addtmp");
    case '-':
        return Builder->CreateFSub(L, R, "subtmp");
    case '*':
        return Builder->CreateFMul(L, R, "multmp");
    case '<':
        L = Builder->CreateFCmpULT(L, R, "cmptmp");
        // Convert bool 0/1 to double 0.0 or 1.0
        return Builder->CreateUIToFP(L, Type::getDoubleTy(*TheContext), "booltmp");
    default:
        return LogErrorV("invalid binary operator");
    }
}

Value* CallExprAST::codegen() {
    // Look up the name in the global module table.
    Function* CalleeF = getFunction(Callee);
    if (!CalleeF)
        return LogErrorV("Unknown function referenced");

    // If argument mismatch error.
    if (CalleeF->arg_size() != Args.size())
        return LogErrorV("Incorrect # arguments passed");

    std::vector<Value*> ArgsV;
    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
        ArgsV.push_back(Args[i]->codegen());
        if (!ArgsV.back())
            return nullptr;
    }

    return Builder->CreateCall(CalleeF, ArgsV, "calltmp");
}

Value* IfExprAST::codegen() {
    Value* CondV = Cond->codegen();
    if (!CondV)
        return nullptr;

    // Convert condition to a bool by comparing non-equal to 0.0.
    CondV = Builder->CreateFCmpONE(
        CondV, ConstantFP::get(*TheContext, APFloat(0.0)), "ifcond");

    Function* TheFunction = Builder->GetInsertBlock()->getParent();

    // Create blocks for the then and else cases.  Insert the 'then' block at the
    // end of the function.
    BasicBlock* ThenBB = BasicBlock::Create(*TheContext, "then", TheFunction);
    BasicBlock* ElseBB = BasicBlock::Create(*TheContext, "else");
    BasicBlock* MergeBB = BasicBlock::Create(*TheContext, "ifcont");

    Builder->CreateCondBr(CondV, ThenBB, ElseBB);

    // Emit then value.
    Builder->SetInsertPoint(ThenBB);

    Value* ThenV = Then->codegen();
    if (!ThenV)
        return nullptr;

    Builder->CreateBr(MergeBB);
    // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
    ThenBB = Builder->GetInsertBlock();

    // Emit else block.
    TheFunction->insert(TheFunction->end(), ElseBB);
    Builder->SetInsertPoint(ElseBB);

    Value* ElseV = Else->codegen();
    if (!ElseV)
        return nullptr;

    Builder->CreateBr(MergeBB);
    // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
    ElseBB = Builder->GetInsertBlock();

    // Emit merge block.
    TheFunction->insert(TheFunction->end(), MergeBB);
    Builder->SetInsertPoint(MergeBB);
    PHINode* PN = Builder->CreatePHI(Type::getDoubleTy(*TheContext), 2, "iftmp");

    PN->addIncoming(ThenV, ThenBB);
    PN->addIncoming(ElseV, ElseBB);
    return PN;
}

// Output for-loop as:
//   ...
//   start = startexpr
//   goto loop
// loop:
//   variable = phi [start, loopheader], [nextvariable, loopend]
//   ...
//   bodyexpr
//   ...
// loopend:
//   step = stepexpr
//   nextvariable = variable + step
//   endcond = endexpr
//   br endcond, loop, endloop
// outloop:
Value* ForExprAST::codegen() {
    // Emit the start code first, without 'variable' in scope.
    Value* StartVal = Start->codegen();
    if (!StartVal)
        return nullptr;

    // Make the new basic block for the loop header, inserting after current
    // block.
    Function* TheFunction = Builder->GetInsertBlock()->getParent();
    BasicBlock* PreheaderBB = Builder->GetInsertBlock();
    BasicBlock* LoopBB = BasicBlock::Create(*TheContext, "loop", TheFunction);

    // Insert an explicit fall through from the current block to the LoopBB.
    Builder->CreateBr(LoopBB);

    // Start insertion in LoopBB.
    Builder->SetInsertPoint(LoopBB);

    // Start the PHI node with an entry for Start.
    PHINode* Variable =
        Builder->CreatePHI(Type::getDoubleTy(*TheContext), 2, VarName);
    Variable->addIncoming(StartVal, PreheaderBB);

    // Within the loop, the variable is defined equal to the PHI node.  If it
    // shadows an existing variable, we have to restore it, so save it now.
    Value* OldVal = NamedValues[VarName];
    NamedValues[VarName] = Variable;

    // Emit the body of the loop.  This, like any other expr, can change the
    // current BB.  Note that we ignore the value computed by the body, but don't
    // allow an error.
    if (!Body->codegen())
        return nullptr;

    // Emit the step value.
    Value* StepVal = nullptr;
    if (Step) {
        StepVal = Step->codegen();
        if (!StepVal)
            return nullptr;
    }
    else {
        // If not specified, use 1.0.
        StepVal = ConstantFP::get(*TheContext, APFloat(1.0));
    }

    Value* NextVar = Builder->CreateFAdd(Variable, StepVal, "nextvar");

    // Compute the end condition.
    Value* EndCond = End->codegen();
    if (!EndCond)
        return nullptr;

    // Convert condition to a bool by comparing non-equal to 0.0.
    EndCond = Builder->CreateFCmpONE(
        EndCond, ConstantFP::get(*TheContext, APFloat(0.0)), "loopcond");

    // Create the "after loop" block and insert it.
    BasicBlock* LoopEndBB = Builder->GetInsertBlock();
    BasicBlock* AfterBB =
        BasicBlock::Create(*TheContext, "afterloop", TheFunction);

    // Insert the conditional branch into the end of LoopEndBB.
    Builder->CreateCondBr(EndCond, LoopBB, AfterBB);

    // Any new code will be inserted in AfterBB.
    Builder->SetInsertPoint(AfterBB);

    // Add a new entry to the PHI node for the backedge.
    Variable->addIncoming(NextVar, LoopEndBB);

    // Restore the unshadowed variable.
    if (OldVal)
        NamedValues[VarName] = OldVal;
    else
        NamedValues.erase(VarName);

    // for expr always returns 0.0.
    return Constant::getNullValue(Type::getDoubleTy(*TheContext));
}

Function* PrototypeAST::codegen() {
    // Make the function type:  double(double,double) etc.
    std::vector<Type*> Doubles(Args.size(), Type::getDoubleTy(*TheContext));
    FunctionType* FT =
        FunctionType::get(Type::getDoubleTy(*TheContext), Doubles, false);

    Function* F =
        Function::Create(FT, Function::ExternalLinkage, Name, TheModule.get());

    // Set names for all arguments.
    unsigned Idx = 0;
    for (auto& Arg : F->args())
        Arg.setName(Args[Idx++]);

    return F;
}

Function* FunctionAST::codegen() {
    // Transfer ownership of the prototype to the FunctionProtos map, but keep a
    // reference to it for use below.
    auto& P = *Proto;
    FunctionProtos[Proto->getName()] = std::move(Proto);
    Function* TheFunction = getFunction(P.getName());
    if (!TheFunction)
        return nullptr;

    // Create a new basic block to start insertion into.
    BasicBlock* BB = BasicBlock::Create(*TheContext, "entry", TheFunction);
    Builder->SetInsertPoint(BB);

    // Record the function arguments in the NamedValues map.
    NamedValues.clear();
    for (auto& Arg : TheFunction->args())
        NamedValues[std::string(Arg.getName())] = &Arg;

    if (Value* RetVal = Body->codegen()) {
        // Finish off the function.
        Builder->CreateRet(RetVal);

        // Validate the generated code, checking for consistency.
        verifyFunction(*TheFunction);

        // Run the optimizer on the function.
        TheFPM->run(*TheFunction, *TheFAM);

        return TheFunction;
    }

    // Error reading body, remove function.
    TheFunction->eraseFromParent();
    return nullptr;
}

//===----------------------------------------------------------------------===//
// Top-Level parsing and JIT Driver
//===----------------------------------------------------------------------===//

static void InitializeModuleAndManagers() {
    // Open a new context and module.
    TheContext = std::make_unique<LLVMContext>();
    TheModule = std::make_unique<Module>("KaleidoscopeJIT", *TheContext);
    TheModule->setDataLayout(TheJIT->getDataLayout());

    // Create a new builder for the module.
    Builder = std::make_unique<IRBuilder<>>(*TheContext);

    // Create new pass and analysis managers.
    TheFPM = std::make_unique<FunctionPassManager>();
    TheLAM = std::make_unique<LoopAnalysisManager>();
    TheFAM = std::make_unique<FunctionAnalysisManager>();
    TheCGAM = std::make_unique<CGSCCAnalysisManager>();
    TheMAM = std::make_unique<ModuleAnalysisManager>();
    ThePIC = std::make_unique<PassInstrumentationCallbacks>();
    TheSI = std::make_unique<StandardInstrumentations>(*TheContext,
        /*DebugLogging*/ true);
    TheSI->registerCallbacks(*ThePIC, TheMAM.get());

    // Add transform passes.
    // Do simple "peephole" optimizations and bit-twiddling optzns.
    TheFPM->addPass(InstCombinePass());
    // Reassociate expressions.
    TheFPM->addPass(ReassociatePass());
    // Eliminate Common SubExpressions.
    TheFPM->addPass(GVNPass());
    // Simplify the control flow graph (deleting unreachable blocks, etc).
    TheFPM->addPass(SimplifyCFGPass());

    // Register analysis passes used in these transform passes.
    PassBuilder PB;
    PB.registerModuleAnalyses(*TheMAM);
    PB.registerFunctionAnalyses(*TheFAM);
    PB.crossRegisterProxies(*TheLAM, *TheFAM, *TheCGAM, *TheMAM);
}

static void HandleDefinition() {
    if (auto FnAST = ParseDefinition()) {
        if (auto* FnIR = FnAST->codegen()) {
            fprintf(stderr, "Read function definition:");
            FnIR->print(errs());
            fprintf(stderr, "\n");
            ExitOnErr(TheJIT->addModule(
                ThreadSafeModule(std::move(TheModule), std::move(TheContext))));
            InitializeModuleAndManagers();
        }
    }
    else {
        // Skip token for error recovery.
        getNextToken();
    }
}

static void HandleExtern() {
    if (auto ProtoAST = ParseExtern()) {
        if (auto* FnIR = ProtoAST->codegen()) {
            fprintf(stderr, "Read extern: ");
            FnIR->print(errs());
            fprintf(stderr, "\n");
            FunctionProtos[ProtoAST->getName()] = std::move(ProtoAST);
        }
    }
    else {
        // Skip token for error recovery.
        getNextToken();
    }
}

static void HandleTopLevelExpression() {
    // Evaluate a top-level expression into an anonymous function.
    if (auto FnAST = ParseTopLevelExpr()) {
        if (FnAST->codegen()) {
            // Create a ResourceTracker to track JIT'd memory allocated to our
            // anonymous expression -- that way we can free it after executing.
            auto RT = TheJIT->getMainJITDylib().createResourceTracker();

            auto TSM = ThreadSafeModule(std::move(TheModule), std::move(TheContext));
            ExitOnErr(TheJIT->addModule(std::move(TSM), RT));
            InitializeModuleAndManagers();

            // Search the JIT for the __anon_expr symbol.
            auto ExprSymbol = ExitOnErr(TheJIT->lookup("__anon_expr"));

            // Get the symbol's address and cast it to the right type (takes no
            // arguments, returns a double) so we can call it as a native function.
            double (*FP)() = ExprSymbol.getAddress().toPtr<double (*)()>();
            fprintf(stderr, "Evaluated to %f\n", FP());

            // Delete the anonymous expression module from the JIT.
            ExitOnErr(RT->remove());
        }
    }
    else {
        // Skip token for error recovery.
        getNextToken();
    }
}

/// top ::= definition | external | expression | ';'
static void MainLoop() {
    while (true) {
        fprintf(stderr, "ready> ");
        switch (CurTok) {
        case tok_eof:
            return;
        case ';': // ignore top-level semicolons.
            getNextToken();
            break;
        case tok_def:
            HandleDefinition();
            break;
        case tok_extern:
            HandleExtern();
            break;
        default:
            HandleTopLevelExpression();
            break;
        }
    }
}

//===----------------------------------------------------------------------===//
// "Library" functions that can be "extern'd" from user code.
//===----------------------------------------------------------------------===//

#ifdef _WIN32
#define DLLEXPORT __declspec(dllexport)
#else
#define DLLEXPORT
#endif

/// putchard - putchar that takes a double and returns 0.
extern "C" DLLEXPORT double putchard(double X) {
    fputc((char)X, stderr);
    return 0;
}

/// printd - printf that takes a double prints it as "%f\n", returning 0.
extern "C" DLLEXPORT double printd(double X) {
    fprintf(stderr, "%f\n", X);
    return 0;
}

//===----------------------------------------------------------------------===//
// Main driver code.
//===----------------------------------------------------------------------===//


int main() {
    InitializeNativeTarget();
    InitializeNativeTargetAsmPrinter();
    InitializeNativeTargetAsmParser();

    // Install standard binary operators.
    // 1 is lowest precedence.
    BinopPrecedence['<'] = 10;
    BinopPrecedence['+'] = 20;
    BinopPrecedence['-'] = 20;
    BinopPrecedence['*'] = 40; // highest.
    // Prime the first token.
    fprintf(stderr, "ready> ");
    getNextToken();

    TheJIT = ExitOnErr(KaleidoscopeJIT::Create());

    InitializeModuleAndManagers();

    // Run the main "interpreter loop" now.
    MainLoop();

    return 0;
}
